The increased demand for data communication and the remarkable growth of the Internet have resulted in increased demand for communication capability within metropolitan areas. There has also been an equally large increase in demand for communication capability between large metropolitan areas. Optical communication systems using a network of fiber optic cables are being developed and installed to meet this increased demand.
The data transmission capacity of fiber optic cables and fiber optic networks has been substantially increased as a result of wavelength division multiplexing (WDM) and dense wavelength division multiplexing (DWDM). Within WDM and DWDM systems, optical signals assigned to different wavelengths are combined (multiplexed) into a multiple wavelength signal for transmission over a single fiber optic cable or other suitable signal carrier or waveguide. A typical DWDM system modulates multiple data streams on to different portions of the light spectrum. For example, one data stream may have an assigned wavelength of 1534 nanometers (nm) and the next data stream may have an assigned wavelength of 1543.8 μm. The required spacing between assigned wavelengths is generally established by International Telecommunications Union (ITU) specifications. These spacings include 0.4 nm and 0.8 nm.
Demultiplexing, the reverse process of multiplexing, typically refers to the separation of a multiple wavelength signal transmitted by a single fiber optic cable or other suitable waveguide into constituent optical signals for each wavelength. Each optical signal may be further processed to obtain the associated data stream or other information. Both multiplexing and demultiplexing are required for satisfactory operation of WDM and DWDM systems. Multiplexing and demultiplexing of optical signals in conventional DWDM systems are typically performed by two separate, relatively expensive and difficult to manufacture optical devices.